Flaws in Microsoft VM. Fix now

Patchwork quilt

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Microsoft has alerted the world+dog to a trio of vulns in its implementation of Java Virtual Machine. The most serious enables an attacker to gain "complete control" over a victim's system. So get patching now.

In an advisory, the company warns that the flaws to Microsoft VM, which ships as part of most versions of Windows and IE, are a critical risk to users.

First, there's a flaw in a class which supports the use of XML by Java applications. This is supposed to differentiate between trusted and untrusted applets - except it doesn't, allowing any old applet to take "virtually any desired action on a user's system".

The second vulnerability involves Java Database Connectivity (JDBC) classes which enable Java applications to connect to and use data from a wide variety of sources. The vulnerability results because of a flaw in the way the classes vet a request to load and execute a DLL on a user's system.

However, it's possible to spoof this check with a malformed request, which allows crackers to load and execute any old DLL on a victim's system, with potentially unpleasant consequences.

The last flaw also involves JDBC classes, and results because "certain functions in the classes don't correctly validate handles that are provided as input", MS explains.

One straightforward use of this flaw, Redmond helpfully explains, would be to supply invalid data instead of an actual handle when calling such a function; this would cause IE to fail.

The exploit scenarios for unprotected users are all too familiar.

An attacker would either create a web page which, when opened, exploits the desired vulnerability, or construct a maliciously-formated HTML mail.

Setting up email clients to open HTML emails in Restricted Sites Zone guards against the risk; or admins could filter out mobile code entirely, MS suggests. ®